Chairs of this type are known in various embodiments. Thus, German Offenlegungsschrift 3,741,472 illustrates and describes a chair in which the seat is mounted pivotably at the front end of the bracket and the back rest is attached to the top end of the column so as to be able to pivot via a bow-shaped piece. A leg spring is fastened to the bracket and supports the rear region of the seat, and the back rest, in a spring-mounted manner. Another solution of the type mentioned, but in which an entirely different concept was adopted, is illustrated in European Patent 105,955. According to this patent, the seat is divided transversely into a front and rear seat part. The front seat part is fastened rigidly to the bracket while the rear seat part is supported via a leg spring fastened to the bracket and to the top end of the column. The back rest is fastened to the rear seat part and to the column via connecting rods and transition pieces.
Although, in general aspects of functionality and ergonomics are of primary importance in chair structures of the present type, there is also a considerable need for sturdy and simple solutions which can be produced at relatively low cost. From this point of view, the chair disclosed in European Patent 105,955 appears to be less favorable as it has a large number of shafts, joints, springs and other moving structural parts, which can result in high manufacturing and assembly cost and, as parts subject to wear, form a fundamental source of disturbance.